JP5748333B2 - Electric heating biomass gasifier - Google Patents

Description

  The present invention relates to biomass gasification technology, and in particular, by drying, pyrolyzing, and gasifying biomass with electric thermal energy, ordinary people gasify a relatively small amount of various biomass at the biomass generation point. This is related to technology that can be used for power generation.

Woody biomass such as thinned wood and milled wood, herbaceous biomass such as rice straw, and waste biomass such as food manufacturing residues such as okara have moved from simple incineration to use for incineration power generation. Many technologies have been proposed for use in liquid fuel synthesis and power generation after conversion to combustible gas.
Conventional biomass gasification technology mainly consists of technology that applies a blast furnace that produces pig iron from iron ore and technology that is derived from the concept of blast furnace. As an example, the updraft fixed bed system is a technique in which biomass is introduced from above and hot air and water vapor are continuously introduced from below. In this example, biomass burns in the lower zone in the furnace and oxygen is consumed, biomass pyrolysis and high-temperature superheated steam generation are performed with combustion heat, water gas is generated with the elevated high-temperature superheated steam, and biomass is formed at the top. Is dried (Non-patent Document 1). In this system, the input biomass had a dual role as a fuel for obtaining heat and a role as a raw material for water gas.

As conventional techniques, various types of gasification furnaces as well as fixed beds and fluidized beds have been proposed. All of these were based on a common technology base in that pyrolysis and gasification were performed using the thermal energy obtained by burning biomass. Because it performs exothermic reaction and endothermic reaction at the same time at a little distance in the same space, it requires advanced skills to control the reaction well. The following is an example of the control method (Non-Patent Document 1).
(1) The biomass gasification rate is controlled by the amount of oxidant (air or oxygen) supplied to the gasification furnace. When the ratio of oxygen and water vapor to be added is kept constant and the oxygen partial pressure is controlled to be constant, the reaction rate in the furnace becomes constant and the temperature becomes constant.
If the reaction rate increases, the gas flow rate for combustion and pyrolysis will increase significantly, causing various adverse effects.
(2) The temperature of the combustion zone is controlled by the amount of water vapor blown from the furnace bottom. That is, the temperature is controlled by increasing or decreasing the heat capacity by increasing or decreasing the amount of steam blown.
However, since water vapor is not only a temperature control function but also a reaction product of a water gasification reaction that generates hydrogen and carbon monoxide, it needs to be considered.
This kind of operation is similar to the control of pot-fired combustion once the biomass is ignited, so it balances the exothermic and endothermic reactions and runs away or extinguishes as a whole system. It is important to maintain a stable state. It varies depending on the amount of oxygen and water supplied, but it is also greatly affected by the type of biomass because the content and water content differ. Therefore, the control of the reaction in the furnace in the prior art is based on a skill based on a high level understanding of events occurring in the furnace.
For these reasons, a technique has been disclosed in which pyrolysis by heating biomass and gasification of a product formed by pyrolysis are separately performed. In these technologies, biomass is first heated to produce carbides, pyrolysis gas, and pyrolysis tar. After the carbide is taken out and pulverized, combustible gas is produced by high-temperature superheated steam together with pyrolysis gas and pyrolysis tar. (Patent Document 1).

The above is a technique for partially oxidizing biomass by heating air or a mixed gas of oxygen and water vapor, but from the beginning, a technique for gasifying in an airless atmosphere containing no oxidant such as air has also been disclosed.
One example is that the biomass is first reductively heated in an airless atmosphere to produce pyrolysis gas and carbide, and then the pyrolysis gas is reformed with superheated steam produced by burning the carbide to produce water gas. (Patent Document 2).
This technology can also be controlled more easily by separating it from the pyrolysis process of biomass and the reforming process of pyrolysis products by superheated steam.
In addition, a technology has been proposed in which biomass is pulverized and mixed with high-temperature superheated steam in a furnace to instantly cause pyrolysis and gasification. This technology increases the chances of encountering powdered biomass floating in the air and superheated water vapor molecules, so that a large amount of superheated water vapor needs to be sent as a physical vehicle, resulting in the need for double the amount of water in the biomass ( Non-patent document 2).
As described above, it goes without saying that in the technology of burning biomass and using it as a heat energy source, it was assumed that the applied biomass was a material useful as a fuel. Woody biomass and herbaceous biomass were suitable materials.
However, other biomass produced in large quantities every day is not necessarily suitable as fuel. For example, coffee mash or okara containing several tens of percent of fats and oils, it is clear that the amount of heat as fuel is completely different from that of vegetable residues even with the same food biomass. In addition, depending on the content, a large amount of soot and tar is generated by pyrolysis, so it is important to perform pyrolysis under optimum conditions.
In this way, biomass that is inappropriate as a fuel has been made an “implicit excluder” as a material for gasification.

Japanese Patent No. 3914474 JP 2004-83340 A Japanese Patent Laid-Open No. 9-245938

“Development of biomass and waste gasifier”, Mitsui Engineering & Shipbuilding Technical Report, No.185 (2005-6) “Development of biomass fuel production technology and promotion of utilization“ demonstration by No. 3 agriculture and forestry biomass ””, www.q-biomass.jp/report/20091028-02.pdf, dated October 21, 2009

An object of the present invention is to realize an apparatus technology that can be used for gasification even by ordinary people for various types of biomass. From this point of view, the following problems existed in the prior art.
The first problem to be solved is that, in the conventional biomass gasification technology, both the thermal energy required for pyrolysis of biomass and the thermal energy required for superheated steam generation are both raw materials for gasification. It is a point that was obtained by burning biomass.
For this reason, the entire process of gasification is a continuous flow work process, and the integrated control of the entire reaction system requires a very high level of technology, so it has been assumed to be operated by a specialist. That is, it has been difficult to generalize or spread the technology.
A second problem to be solved is that the gasification reaction system sequentially advances individual reactions, so that a plant-type facility in which reaction devices are arranged in series is provided.
For this reason, the facility has become a large facility that cannot be moved, and it has not been possible to achieve the original purpose of gasification at each biomass generation point without transportation costs.

  In the present invention, the space inside the gasification furnace is directly electrically heated. Therefore, the thermal decomposition reaction of biomass and the subsequent gasification reaction can be performed with high accuracy by adjusting the furnace temperature to a predetermined temperature by electrical control. Since it can be performed under controlled temperature conditions, the most important feature is to realize an electrically heated biomass gasifier that can be operated by ordinary people according to the type and moisture content of biomass.

  The present invention has an advantage of realizing an electrically heated biomass gasification apparatus that can be operated and used by a general person according to the type of biomass at each biomass generation point.

FIG. 1 is an explanatory diagram showing a configuration of an electrically heated biomass gasifier. Example 1 FIG. 2 is an explanatory diagram showing the configuration of the electrically heated biomass gasifier. (Example 2) FIG. 3 is a graph showing changes in temperature and water content in the batch mode of the electrically heated biomass gasifier. (Example 1, Example 2)

  Superheated steam with electric thermal energy is used to generate combustible biogas by performing pyrolysis and gasification according to the type of biomass, while minimizing the production of by-products such as carbide residues and tar. It was realized by producing and acting on biomass.

  According to the first aspect of the present invention, there is provided an electrically heated biomass gasification apparatus comprising a gasification furnace for gasifying biomass, a steam generating means, a steam supply adjusting means, and an electric heating element in the gasification furnace. , Heating the steam supplied into the furnace to continuously generate superheated steam, heating the interior space of the furnace, electrical heating control means, and a plurality of gasification furnace measurement points Temperature sensors (multiple) for detecting the temperature, pressure control means for adjusting the pressure inside the gasifier by adjusting the gas discharge rate from the gasifier, and the pressure sensor for detecting the pressure inside the gasifier And systematically controlling the steam supply adjusting means, the electric heating control means, and the atmospheric pressure adjusting means so that the temperature and the atmospheric pressure in the gasifier take predetermined values according to the type of biomass and the processing mode of the biomass. System control means and Ri made, and dried biomass with superheated steam generated by electrical heating and pyrolysis and gasification, and generates a combustible gas.

  According to a second aspect of the present invention, there is provided an electric heating biomass gasification apparatus, wherein the electric heating means of the electric heating biomass gasification apparatus according to the first aspect includes an electric resistance heater disposed in a gasification furnace, The steam supplied to the inside is heated to continuously generate superheated steam, and the furnace space is heated.

  According to a third aspect of the present invention, there is provided an electric heating biomass gasification apparatus according to the first aspect, wherein the electric heating means of the electric heating biomass gasification apparatus according to the first aspect uses a conductor disposed in the gasification furnace outside the gasification furnace. It is characterized by electromagnetic induction by an electromagnetic induction heater arranged in the above, heating the steam supplied into the furnace to continuously generate superheated steam and heating the space in the furnace.

  According to a fourth aspect of the present invention, there is provided an electric heating type biomass gasification apparatus in which the electric conductor disposed in the gasification furnace in the electric heating means of the electric heating type biomass gasification apparatus according to the third aspect has a lump shape. Thus, it also has a function as a heat medium that can be repeatedly used in a gasification furnace.

  FIG. 1 is an explanatory diagram showing an overall configuration of Example 1 of an electrically heated biomass gasifier according to the present invention, taking an updraft type fixed bed type as an example.

  In Example 1, biomass 2 is charged from above gasifier 1. Further, water vapor or high temperature water vapor 3 flows from below the gasification furnace 1.

  An electric resistance heater 4 is disposed at the bottom of the gasification furnace 1 and heats the inflowing steam or the high temperature steam 3 to generate superheated steam.

In the gasification furnace 1, temperature sensors (not shown) are provided at positions corresponding to at least each zone (described later) to monitor the furnace temperature. The steam or the high temperature steam 3 continuously flows into the furnace and is continuously heated by the electric resistance heater 4 to become superheated steam.
The temperature of the superheated steam to be generated is determined by the power value of the electric resistance heater 4 and the inflow amount (inflow rate) per unit time of the steam or the high temperature steam 3. Therefore, an optimum superheated steam temperature is set in advance according to the type of biomass, and the electric power value of the electric resistance heater 4 and the steam are set so that the superheated steam generated in the heating zone (c) becomes that temperature. Alternatively, the inflow speed of the high temperature steam 3 is determined. The temperature of the superheated steam generated in the heating zone (c) is detected by a temperature sensor arranged in this zone. The temperature of the superheated steam is set to 500 ° C. or higher corresponding to the type of biomass.
As the electrical resistance heater 4, a porous electrical resistance heater disclosed in Patent Document 3 can be applied.

  Since the biomass 2 contains moisture, the thermal energy held by the superheated steam is consumed for drying the biomass 2 until the moisture vaporization is completed. Meanwhile, the temperature of the superheated steam in contact with the biomass 2 does not rise to a predetermined temperature.

The drying of the biomass 2 is completed sequentially from the vicinity of the heating zone (c), and the temperature of the superheated steam in the vicinity rises to a predetermined temperature, so that the pyrolysis of the dried biomass 2 begins and the water gasification reaction continues. To do. Thus, in the gasification furnace 1, the drying zone (a) of the biomass 2 and the thermal decomposition / gasification zone (b) are formed above the heating zone (c).
At this time, as the temperature rises, the volume of superheated steam increases, the atmospheric pressure in the gasification furnace 1 rises, and the supplied steam 3 becomes high-pressure and high-temperature steam, while the outflow amount of the exhaust gas 5 increases. The atmospheric pressure in the gasification furnace 1 is detected by an atmospheric pressure sensor (not shown) arranged in the furnace.

Here, the difference from the prior art is that the water vapor or high-temperature water vapor 3 flowing into the gasification furnace 1 does not contain an oxidant such as air or oxygen. Therefore, biomass 2 does not burn. The pyrolysis and gasification of the biomass 2 is not a combustion heat energy, but a so-called “steamed state” by radiant heat transfer of the electric resistance heater 4, radiant heat transfer, condensation heat transfer and convection heat transfer of high-temperature superheated steam. Done. The fact that all heating energy is derived from electrical energy means that the heat treatment of biomass 2 can be controlled electrically, in other words, it is synonymous with being released from the “Kamawaki” technology that requires advanced skills. It is.
That is, the present invention is freed from the combustion control operation based on the subtle adjustment of the biomass type, the oxidant inflow amount, and the water vapor inflow amount in the prior art, and the superheated steam corresponding to the type of biomass. All that was needed was the temperature setting.

As described above, the “continuous mode” in which the biomass is continuously or intermittently input has been described. However, in the present invention, the “batch mode” in which the biomass is batch-input and processed is also possible. Conventional combustion heat utilization technology cannot perform batch processing because pyrolysis stops when the supply of biomass as fuel is interrupted. Since batch processing is suitable for small-scale processing, it is most suitable for applications in which processing is performed in small portions at the biomass generation point.
In the case of the batch mode, it is effective to divide the biomass for one input into a drying stage, a pyrolysis stage, and a gasification stage and perform profile control (see FIG. 3). By setting an appropriate superheated steam temperature for each stage, the production of by-products such as tar can be minimized and the yield of combustible gas can be maximized.
(1) Drying stage: biomass is previously dried in order to minimize the generation of tar and pyrolysis char. That is, the biomass is dried by generating superheated steam at 200 ° C. or lower.
(2) Pyrolysis stage: When the drying is completed, the temperature of the superheated steam rises to the temperature at the time of administration. Next, the heated steam is raised to, for example, about 550 ° C. and enters the pyrolysis stage. At this time, since the atmospheric pressure also increases, the inside of the gasification furnace is adjusted to a predetermined temperature and atmospheric pressure by the system control means. The pyrolysis gas generated in the pyrolysis stage is discharged together with superheated steam, and pyrolysis char remains in the furnace.
(3) Gasification stage: Finally, the temperature of the superheated steam is raised again to about 800 ° C., enters the gasification stage, and the remaining pyrolysis char is gasified.

Since the ash which is the residue of gasification accumulates in the bottom part (c) of the gasification furnace 1, this is taken out (6).
Part of the pyrolysis gas generated by pyrolysis is reformed with water vapor to become a water gas. Most of the pyrolysis tar adheres to the biomass 2 deposited in the drying zone (a) and is pyrolyzed in the pyrolysis / gasification zone (b).
The exhaust gas 5 from the gasification furnace 1 contains pyrolysis gas, water gas, pyrolysis tar, atomized char, fly ash, volatile components, and superheated steam.
The pyrolysis gas, pyrolysis tar, and atomized char therein are reformed by superheated steam when passing through the reforming furnace 7 maintained at 800 ° C. or more to become water gas, and the remaining atomized char remains. The fly ash is purified by the gas purification system 8, and the superheated steam containing water-soluble components is removed in the heat exchanger 9.

The clean biogas thus obtained is a combustible gas composed of hydrogen, carbon monoxide, methane, carbon dioxide, etc., and performs gas power generation by a gas power generation system (10) including a gas engine and a generator. .
The obtained electric power is stored in the secondary battery (11), and a part of the electric power is used as necessary electric power for the apparatus such as the electric resistance heater 4.

  FIG. 2 is an explanatory diagram showing an overall configuration of Example 2 of the electrically heated biomass gasifier according to the present invention, using an updraft type fixed bed type as an example.

  In Example 2, the biomass 2 and the massive conductor 3 are charged from above the gasifier 1. Further, water vapor or high temperature water vapor 4 flows from below the gasification furnace 1. The conductor 3 is deposited on the bottom of the gasification furnace 1 by its own weight to form a heating zone (c).

  An electromagnetic induction heater 5 having a high frequency power source and an exciting coil is disposed outside the bottom of the gasification furnace 1, and heats up the conductor 3 deposited on the bottom of the gasification furnace 1 through the heat insulating insulator wall of the gasification furnace 1. The inflowing steam or the high temperature steam 4 is heated to generate superheated steam.

In the gasification furnace 1, temperature sensors (not shown) are provided at positions corresponding to at least each zone (described later) to monitor the furnace temperature. The steam or high temperature steam 4 flowing into the furnace is heated in the heating zone (c) to become superheated steam.
The temperature of the superheated steam to be generated is determined by the power value of the electromagnetic induction heater 5 and the inflow amount (inflow rate) per unit time of the steam or the high temperature steam 4. Therefore, an optimal superheated steam temperature is set in advance according to the type of biomass, and the power value of the electromagnetic induction heater 5 and the steam or high temperature are set so that the superheated steam generated in the heating zone (c) becomes that temperature. The inflow rate of the water vapor 4 is determined. The temperature of the superheated steam generated in the heating zone (c) is detected by a temperature sensor arranged in this zone. The temperature of the superheated steam is set to 500 ° C. or higher corresponding to the type of biomass.

  Since the biomass 2 contains moisture, the thermal energy held by the superheated steam is consumed for drying the biomass 2 until the moisture vaporization is completed. Meanwhile, the temperature of the superheated steam in contact with the biomass 2 does not rise to a predetermined temperature.

Drying of the biomass 2 is sequentially completed from the vicinity of the conductor 3, and the temperature of the adjacent superheated steam rises to a predetermined temperature. Therefore, thermal decomposition of the dried biomass 2 starts and water gasification continues. Thus, in the gasification furnace 1, the drying zone (a) of the biomass 2 and the thermal decomposition / gasification zone (b) are formed above the heating zone (c).
At this time, as the temperature rises, the volume of superheated steam increases, the atmospheric pressure in the gasification furnace 1 rises, and the supplied steam 4 becomes high-pressure high-temperature steam, while the outflow amount of the exhaust gas 6 increases. The atmospheric pressure in the gasification furnace 1 is detected by an atmospheric pressure sensor (not shown) arranged in the furnace.

Here, the difference from the prior art is that the steam or high-temperature steam 4 flowing into the gasifier 1 does not contain an oxidant such as air or oxygen. Therefore, biomass 2 does not burn. Pyrolysis and gasification of the biomass 2 is performed in a so-called “steamed state” by radiant heat transfer of the conductor 3, radiant heat transfer, condensation heat transfer, and convective heat transfer of the high-temperature superheated steam instead of combustion heat energy. . The fact that all heating energy is derived from electrical energy means that the heat treatment of biomass 2 can be controlled electrically, in other words, it is synonymous with being released from the “Kamawaki” technology that requires advanced skills. It is.
That is, the present invention is freed from the combustion control operation based on the subtle adjustment of the biomass type, the oxidant inflow amount, and the water vapor inflow amount in the prior art, and the superheated steam corresponding to the type of biomass. All that was needed was the temperature setting.

As described above, the “continuous mode” in which the biomass is continuously or intermittently input has been described. However, in the present invention, the “batch mode” in which the biomass is batch-input and processed is also possible. Conventional combustion heat utilization technology cannot perform batch processing because pyrolysis stops when the supply of biomass as fuel is interrupted. Since batch processing is suitable for small-scale processing, it is most suitable for applications in which processing is performed in small portions at the biomass generation point.
In the case of the batch mode, it is effective to divide the biomass for one input into a drying stage, a pyrolysis stage, and a gasification stage and perform profile control (see FIG. 3). By setting an appropriate superheated steam temperature for each stage, the production of by-products such as tar can be minimized and the yield of combustible gas can be maximized.
(1) Drying stage: biomass is previously dried in order to minimize the generation of tar and pyrolysis char. That is, the biomass is dried by generating superheated steam at 200 ° C. or lower.
(2) Pyrolysis stage: When the drying is completed, the temperature of the superheated steam rises to the temperature at the time of administration. At this time, since the atmospheric pressure also increases, the inside of the gasification furnace is adjusted to a predetermined temperature and atmospheric pressure by the system control means. The pyrolysis gas generated in the pyrolysis stage is discharged together with superheated steam, and pyrolysis char remains in the furnace.
(3) Gasification stage: Finally, the temperature of the superheated steam is raised again to about 800 ° C., enters the gasification stage, and the remaining pyrolysis char is gasified.

Since the ash which is the residue of gasification is deposited on the bottom (c) of the gasification furnace 1, it is taken out together with the used conductor 3 (7). The used conductor 3 is reused after cleaning dirt mainly composed of pyrolysis tar adhering to the surface by heat treatment or the like.
Part of the pyrolysis gas generated by pyrolysis is reformed with water vapor to become a water gas. Most of the pyrolysis tar adheres to the biomass 2 deposited in the drying zone (a) and is pyrolyzed in the pyrolysis / gasification zone (b).
The exhaust gas 6 from the gasification furnace 1 contains pyrolysis gas, water gas, pyrolysis tar, atomized char, fly ash, volatile components, and superheated steam.
The pyrolysis gas, pyrolysis tar, and atomized char therein are reformed by superheated steam when passing through the reforming furnace 8 maintained at 800 ° C. or higher to become water gas, and the remaining atomized char remains. The fly ash is purified by the gas purification system 9, and the superheated steam containing water-soluble components is removed in the heat exchanger 10.

The clean biogas obtained in this way is a combustible gas composed of hydrogen, carbon monoxide, methane, carbon dioxide, etc., and performs gas power generation by a gas power generation system (11) including a gas engine and a generator. .
The obtained electric power is stored in the secondary battery (12), and a part of the electric power is used as necessary electric power for the apparatus such as the electromagnetic induction heater 5.

As mentioned above, although the function of the gasification furnace 1 was demonstrated using the updraft type fixed bed type | mold as an example, as long as biomass of this invention is thermally decomposed with the electrical thermal energy generated in the furnace, the gasification furnace 1 Needless to say, the type may be a fluidized bed type equipped with a stirring means, or a gasification furnace of another type may be adopted.
Similarly, the present invention may be applied to a cogeneration system that reuses exhaust heat of gas power generation as long as biomass is thermally decomposed by electrical thermal energy generated in the furnace.

  By generating electrical thermal energy in the furnace and pyrolyzing and gasifying the biomass, it is no longer necessary to use the heat of combustion of the biomass, so that the general public can generate combustible biogas from the biomass at the point of biomass generation. It can be generated and used for power generation.

DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Biomass 3 Conductor 4 Steam or high temperature steam 5 Electromagnetic induction heater 6 Exhaust gas 8 Reforming furnace 11 Gas power generation system

Claims (4)

A gasification furnace for gasifying biomass;
Water vapor generating means;
Water vapor supply control means;
An electric heating means is disposed in the gasification furnace, the steam supplied to the furnace is heated to continuously generate superheated steam, and the furnace heating space is heated.
Electric heating control means;
A temperature sensor (multiple) for detecting the temperature of the gasification furnace measurement points (multiple),
A pressure adjusting means for adjusting the pressure inside the gasifier by adjusting the amount of gas discharged from the gasifier;
A pressure sensor for detecting the pressure in the gasifier,
Depending on the type of biomass, the continuous mode in which the biomass is continuously or intermittently input, and the batch mode in which the biomass is batch input and processed , steam and steam are controlled so that the temperature and pressure in the gasifier take predetermined values. A system control means for systematically controlling the supply adjusting means, the electric heating control means and the atmospheric pressure adjusting means,
An electrically heated biomass gasifier characterized in that biomass is dried, pyrolyzed and gasified by superheated steam generated by electric heating to generate a combustible gas.   The electric heating means is characterized in that an electric resistance heater is disposed in the gasification furnace, the steam supplied to the furnace is heated to continuously generate superheated steam, and the furnace space is heated. The electrically heated biomass gasifier according to claim 1.   The electric heating means electromagnetically induces a conductor disposed in the gasification furnace by an electromagnetic induction heater disposed outside the gasification furnace, and heats the steam supplied into the furnace to continuously generate superheated steam. In addition, the electrically heated biomass gasifier according to claim 1, wherein the furnace space is heated.   4. The electric heater disposed in the gasification furnace in the electric heating means is in the form of a lump, and also has a function as a heat medium that can be repeatedly used in the gasification furnace. The electrically heated biomass gasifier described.

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